The leaders of Democratic Republic of Congo and Rwanda will attend a regional summit in Uganda on Saturday after rebels seized the main eastern Congolese city of Goma, Ugandan officials said Thursday.
African Union Commission chairwoman Nkosazana Dlamini-Zuma will also attend the extraordinary summit of the 11-member regional bloc, the International Conference on the Great Lakes Region (ICGLR).
DR Congo's Joseph Kabila and rival Rwandan counterpart Paul Kagame -- whom the United Nations accuses of backing the M23 rebels who seized the city of Goma on Tuesday, claims Kigali rejects -- will be at the Kampala summit.
"They are attending," said Asuman Kiyingi, Ugandan state minister for regional cooperation. "It would be meaningless without them."
Dlamini-Zuma will attend as part of AU "efforts aimed at finding a lasting solution to the crisis in the North Kivu region of the DRC", the pan-African bloc said in a statement.
Kabila and Kagame met on Tuesday and Wednesday, hours after the capture of Goma, issuing a joint statement with Ugandan President Yoweri Museveni calling for the M23 to stop its offensive and pull out of Goma.
The ICGLR have held multiple summits in recent months on the conflict in eastern DR Congo. None of them resulted in any significant breakthrough.
"We are not going to stop at Goma, we will go as far as Bukavu, Kisangani and Kinshasa," M23 spokesman Vianney Kazarama told a crowd massed at a stadium in Goma a day after the rebels overran the eastern city with little or no resistance from UN or government troops.
Rebels said Wednesday they had also seized the town of Sake, about 20 kilometres (more than 10 miles) northwest of Goma. They vowed to press on southward to Bukavu, the other major city on the border with Rwanda.
Kazarama also demanded that President Joseph Kabila leave power, claiming he was not the legitimate winner of last year's disputed presidential election.
UN envoy Roger Meece accused the rebels of carrying out "summary executions" of local leaders in their advance.
Meece told the UN Security Council that the ethnic Tutsi rebels who launched their uprising in April were trying to set up "a formal administrative or governing structure" in the region.
"We have received numerous reports of targeted summary executions of those who stand in their way, including government and traditional leaders who resist or fail to cooperate with an M23 administrative structure," he said.
Meece said that since the fall of Goma there had been demonstrations in several cities against the UN presence and the government
The United Nations and other humanitarian groups have reported killings, abductions, looting and extortion of civilians and fears of a humanitarian catastrophe were growing as electricity and water supplies dried up.
Violent demonstrations erupted in several DR Congo towns, including Kisangani where protesters targeted the UN base, as well as a church whose pastor was accused of having M23 ties, a resident said.
Six people were also killed in protests in the town of Bunia, a Western aid worker said. The information could not be immediately confirmed.
The M23 has vowed to fight on unless the government in the capital Kinshasa agrees to talks, and as they consolidated their control of Goma, Kazarama called for police and soldiers to join the rebels.
Experts said it was unclear whether the M23 had taken Goma as a stepping stone towards seizing more territory, or simply to gain greater bargaining power with Kabila.
DR Congo Prime Minister Augustin Matata Ponyio said Kinshasa had "lost the battle but not the war", and insisted the country's territorial integrity was "non-negotiable".
The UN defended its peacekeepers after Goma fell, with a spokesman saying a battle for the city would have endangered civilians.
It has around 1,500 "quick reaction" peacekeepers in Goma, part of some 6,700 troops in North Kivu province, backing government forces against the rebels.
The UN Security Council on Tuesday unanimously backed a resolution calling for sanctions against two M23 leaders and an end to all "outside support" for the rebels.
UN Secretary General Ban Ki-moon issued a new condemnation of "grave" human rights violations by the fighters, although retreating government troops have themselves been accused of looting.